Sample scale

ABSTRACT

Spring operated sample scales for use in grain moisture testers to measure a fixed weight of the material under test and including a hopper mounted on four parallel bars for parallel vertical movement with respect to the remainder of the tester, the hopper having automatically actuated doors on the lower wall thereof, are disclosed.

"United States Patent 1151 3,701,390

v 'Fathauer [451 Oct. 31, 1972 1541 SAMPLESCALE I 381;,126 5/1888 Henry ..177/113 40' ,189' 5/1889 Henry ..177/107 .F D 1 ,111. 7 544,803 8/1895 Wilde ..177/112 [7 A g Overton p r i Countryside, 587,680 8/1897 McLeod et 1. ..177/112 Ill. 648,877 5/1900 McLeod =1 al. ..177/1 12 1,152,868 9/1915 Zanone ..177/113 [221 1,164,873 12/1915 Ross ..l77/l06 [63] Continuation of Ser. No. 43,770, June 5, 1970, son

1211 Appl. Na: 199,325

Rented Application D. Primary Examiner-Robert S. Ward, Jr.

Attorney-Pendleton, Neuman, Williams and Anderabandoned.

' [57] ABSTRACT l. ..177 113 177 225 a g Gmg 13/18 601g 13/44 (50182104 Spring operated sample scales for use in gram [58] H d l77/105 107 112 moisture testers to measure a fixed weight of the e o 225 material under. test and including a hopper mounted on four parallel bars for parallel vertical movement with respect to the remainder of the tester, the hopper [56] References Cited having automatically actuated doors on the lower wall UNITED STATES PATENTS thereof, are disclosed.

379,954 3/1888 Hartley ..l77/ 105 14 Claims, 20 Drawing Figures 45 a! 1 ""H Z2 1 1.1 1 1| ,,f K 3 1 :f-' {1:1 1 1"? I t I? 7 IQ l az 1 7- Mm 1 1 W L- l ,u I l I "kg: 3: 22:;22113 l J x i I 1 SAMPLE SCALE This is a continuation of application, Ser. No'. 43,770;filed.lune 5,1970.

such sample scales for use in moisture testers used to. determine the moisture content of various grains of fibrous materials.

In the past many small, portable devices have been known where, in connection with the operation thereof, itwas desired to obtain a sample of material having a predetermined, fixed weight. One'such device 'is the moisture tester disclosed in UIS.' Pat. -No.

3,051,894, entitled Impedance Indicating Instrument, to'D. F. Fathauer which issued'on Aug. 28,

.1962." Thatpatent discloses an apparatus for determinf ing the percentage moisture content of a given amount of grain placed in a grain cell, the given amount usuallybeing a sample of predetermined weight. An electric circuit for another grain moisture tester is disclosed in my copending applicatiomSer. No. 33,326, filed Apr. 30, 1970, and entitled Impedance Measuring Cir- 5 tester having a sample scale to measure a cult. It hasbeen found desirable to include scales within such types of devices so that samples of the desired weight may easily be measured out by the user.

Such sample scales should be characterized by a number of features. They should, of course, yieldaccurate results over a long period of time. They should be of relatively durable construction as they and the devices with which they are associated will often be subject to much physical abuse. They should provide for a relatively simple mode of operation by the user, preferably not calling for the making of any .difficult judgments as to whether a balanced condition exists. Dust and particles generated by the materials weighed in them should have relatively little effect on their operation. They should be of light weight and compact size,simple in design, and economical to manufacture. Further, in scales used with grain moisture testers of the type above referred to, it is desirable that the scales include means for transferring the grain from the scale to the grain cell which distributes and compacts the grainin the cell in a repeatable manner as the accura- SUMMARY OF THE INVENTION In carrying out this invention in one form, a sample scale is'provided including a hopper connected to a relatively fixed supportby a plurality of'parallelly oriented bars, the hopper being restrained from downward movement by springs coupled between it] weight of material.

7 2 Accordingly, it is an object of this invention to provide a sample scale for measuring a predetermined It is an object'ofthis invention to provide a moisture mined weight of the material under test.

It is an object of this invention to provide asample scale having a hopper for receiving the material under test with an automatically operating 'door forming the lower surface thereof. It is an object of this invention to provide a sample scale for measuring a predetermined weight of material which gives a positive indication when the predetermined weight is obtained.

It is anobject of this invention to provide a sample scale and hopper combination wherein the accuracy of the scale is not affected by the distribution of the weighed material within the hopper.

Itis an object of this invention to provide a sample I scale for measuring a predetermined weight of materialwith a high degree of accuracy.

It is an object of this invention to provide a sample scale for measuring a predetermined weight of material characterized by simplicity of construction and operation, economy of manufacture, compact size, light weight, and durability.

Further and additional objects will appear from the description accompanying drawings and appended claims.

DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a first grain moisture tester including a first sample scale of this invention;

FIG. 2 is a plan view of the grain moisture tester of FIG. 1; I I

FIG. 3 is a fragmentary side view of the grain moisture tester of FIG. 1 showing the first sample scale in dotted form; 1

FIG. 4 is a side view of the sample scale of FIG. 3 including those parts of theremainder of the moisture tester which operatively engage the scale;

FIG. 5is an end view of the sample scale of FIG. 3; I

FIG. 6 is a view similar to FIG. 4 showing the operadoor catch mechanism included in the sample scale of FIG. 3; v

FIG. 10 is a detail, cutaway view of the hopper door 7 catch mechanism included in the sample scale of FIG. 3

and the fixed support. A preloaded stop against upward vertical movement of thehopper is provided so that the showing the mechanism in thelocked position with'the door closed; Y Y

FIG. 11 is a detail view similar to FIG. '10 showing mechanism in the locked position with the door open;

FIG. 13 is a detail, cutaway view showing the bearing structure of the support bars included in the sample I scale of FIG. 3;

predeter DESCRIPTION OF THE PREFERRED EMBODIMENTS In the subsequent disclosure this invention will be described in relation, to the provision of sample scales in two separate grain moisture testers. It will be ap-- parent to those skilled in the art, however, that the sample scales of this invention are of much broader appliincluded cation.

A first grain moisture tester including a sample scale of this invention is shown in FIGS. 1 and 2. While not necessary to an understanding of this invention, the overall construction and operation of the tester will be briefly disclosed for the sake of completeness. The tester is of unitary construction and contained within a single housing 12 having disposed on the upper surface thereof a power switch'l4, a balance switch 16, a meter 18, a dial mechanism 20, a sample scale 22 of this invention, an opening 24, and a removable thermometer 26 extending into the interior of housing 12 and a holder therefor 28. The electrical circuitry required for the operation of this invention, not shown, is located within housing 12 beneath dial mechanism and is disclosed in my above-referenced copending application, Ser. No. 33,326 Dial mechanism 20 includes a wheel mechanically connected to both a cylindrical drum 32 and a variable electric circuit element included within the electric circuitry of the tester. Wheel 30 and drum 32 are mounted for rotational movement within housing 12. Drum 32 is located beneath a hairline indicator 34 and has disposed thereon a plurality of scales which give the percentage of moisture of the grain under test, different scales being used alternatively for different grains or for different weight samples of the same grain.

In operation of the moisture tester shown, power switch 14 is first depressed to activate the internal circuit. Balance-switch 16 is then momentarily depressed to bring the internal circuitry to an initial, balance condition or state. A balance condition is known to exist when the indices on meter 18 are at a central location. The sample scale 22 is then used to weigh out a measured amount of grain. Thermometer .26 is removed from its holder 28 and used to measure the temperature of the grain in the hopper. The measured grain is released into a grain cell, not shown, located directly beneath the sample scale. The cell holds the grain in a predetermined physical relationship so that one of its electrical properties may be measured by the-internal circuitry thus giving an indication of its moisture content.

To make the measurement, wheel 30 is adjusted to reb'alance the internal circuit, again observing meter 18. The percentage moisture content may be read underneath hairline indicator 34 from the correct scale on drum 32. If the temperature of the grain is significantly different from the standard temperature used in establishing the scales on drum 34, conveniently 80 F., the indicated moisture content should be adjusted by an amount which may be read from a chart or scale supplied with the tester or, conveniently, printed on the thermometer itself. Drum 32 may have a decimal scale thereon which, when used in connection with various charts supplied with the moisture tester, may be used to determine the moisture content of grains which have not been provided with individual scales on drum 32. Further, weights may be attached to scale 22 when an amount of grain less than that normally used is desired, thus extending the useful range of the instrument. Upon completion of the measurement, the grain is removed from-the tester through opening 24.

The sample scale 22 included in moisture tester 10 is disclosed in FIGS. 3-15. It includes a hopper 40 arranged to receive the material under test and having a door 42 as the lower wall thereof. The hopper is mounted on springs to enable its use as a scale for measuring a predetermined weight, say, for example, 5 ounces, of the material under test. Door 42, allows the grain to be emptied from the hopper and delivered into the grain cell.

Hopper 40 has a first, lower section 44 with an interior surface similar to that of an inverted, truncated pyramid and a second, upper section 46 extending about the periphery of the hopper and extending through an opening 48 in the upper surface 50 of the moisture tester. The lower surface of hopper 40 is open but may be closed by door 42. A ridge 52 is disposed on the outside of, and completely surrounding, upper section 46 but is located beneath surface 50, thereby effecting a seal in opening 48. Door 42 extends across the lower opening of hopper 40 and is hingedly connected thereto as by pins 53 fixedly attached to the hopper and rotatably attached to the door. The hopper 40 may be of unitary construction and is, preferably, of some type of plastic, while door 42 may be metallic.

Hopper 40 has side brackets 54 attached to either side thereof as by screws 56. A support bracket 58 is fixedly attached to the main body of moisture tester l0. Bracket 58 has attached thereto four conical bearing points 60, two disposed on each side thereof; they may preferably be pressed in place to achieve center accuracy and stability. Spring retaining members 62 are also attached to bracket 58, one on either side, and have a,

generally V-shape. Screws 63 are threaded through support members 64 of bracket 58 and bear against spring retaining members 62. An insert 66 is threaded through an opening in each member 62 and has a knifeedge bearing surface 68 on its inner surface. (See FIG. 14.)

Side brackets 54 each have attached thereto bearing points 70, also preferably pressed in place. (See FIG. 13.) The bearing points 70 are spaced in the same relative position as the bearing points 60 on bracket 58. Each side bracket 54 has, additionally, a spring retaining member 72 with an insert 74 threaded through it having a knife-edge interior bearing surface similar to surface 68in insert 66. The interior bearing surface of insert 74 should be positioned relative to bearing points 70 slightly below the position of the interior bearing surface on insert 66, for reasons which will subsequently become apparent.

Two sets of parallel bars, a pair of upper bars 76 and r a pair of lower bars 78, all having the same length, are disposed between the corresponding conical bearing points 60 and 70 on brackets 58 and 54, respectively, one bar of each pair being located on either side of hopper 40. Journals'80, having concave, conical interior surfaces, are provided at both ends of each bar 76 and 78 for receiving conical bearing points 60 and 70. The interior surface or journals 70 must have a slope sufficientlyless than'that of the exterior surface of bearings60 that bars 76 and 78 may change their positions relative to brackets .54 and 58 by. a substantial amount, say, for example, by as much asv 5 degrees from theperpendicular, without causing binding between the bearing points and the journals. (See, particularly, FIG. l-3.) -Additionally, a hollow connecting rod 81 having holes therethrough through which parallel bars 78 are inserted is providedtomaintain the two bars 78 in a fixed, coacting relationship, and preventing flex in the hopper support mechanism about an axis approximately parallel to bars 76 and 78.

Spiral springs 82 are provided to hold the combination of hopper 40, brackets 54 and 58, and bars 76 and 78. together and, additionally, to provide the elastic body required in a spring scale. One end of each spring 82 is placed through an insert 66 on hopper bracket 58 while the second end is placed through an insert 74 on aside bracket 54 so that both ends bear against the knife-edge surfaces of their respective inserts.

lt will, thus, be seen that a structure has been provided wherein a hopper 40 is capable of vertical movement in relation to a relatively fixed member, i.e'., hopper bracket 58,but is restrained from downward movement by springs 82 because of the relative positioning of the knife-edge bearings on which the springs ride. The'structure may thus be used as a conventional spring scale, the distance of downward displacement of the hopper being proportional over at least a limited range to the weight of material placed in thehopper. Additionally, however, in the disclosed structure the hopper is attached to support bracket 58 through a set of parallel bars 76 and 78. The bars and the brackets to which they are attached may be viewed as forming the sides of two parallelograms, one on either side of the hopper. As hopper 40 is displaced vertically relative to hopper bracket 58, the opposite sides of both parallelograms remain parallel, and hopper 40 is maintained in a verticalposition, parallel to the support bracket 58. This insures that the scale will give accurate results no matter how the grain being weighed is distributed within the scale.

The modulus of elasticity and length of springs 82 may be chosen so that bars 76 and 78 will be horizontal when the desired measured weight of material is placed in hopper 40. Thus the desired weight will be achieved when brackets 54 are at their maximum horizontal displacement from bracket 58, providing an over center action for the scale thereby substantially increasing its sensitivity. The scale maybe calibrated by adjustment of screws 63 which, in turn, alters the location of spring support members 62 and thus the vertical position of the bearing points at the ends of spring 82 connected to bracket 58. In other embodiments of this invention it may, be desirable to provide an additional adjustment for the horizontal position of the bearing points so that the sensitivity of the scale might also be readily varied.

Turning now to the hopper door catch mechanism, hopper has two parallel support walls protruding from a side of hopper 40, in this embodiment from that side removed from support bracket 58. A nylon, generally S-shaped, catch lever 92 is provided having a hole 94 therethrough in the upper portion thereof. A pin 96 passes through hole 94 and corresponding holes in support walls 90 to pivotally support the catch lever between the support walls. A spring retaining trough 98 is included on the side of catch lever 92 adjacent hopper 40 and above hole 94. A generally W-shaped spring 100 is provided and is retained between support walls 90 for resiliently forcing the upper portion of catch lever 92 away from hopper 40 and the lower portion toward hopper 40. The catch lever has a door release dog 102 and a door retaining dog 104 on the upper and lower, respectively, extremities thereof. Dog 104 includes a beveled surface 108 on its lower side.

Door 42 includes a latching extension 110 forengagement withdoor retaining dog 104. The extension includes an oblique surface 112 for engagement with beveled surface 108 on dog 104, as will be subsequently apparent. Surface 112 may, conveniently, be formed by folding back an extremity of extension 1 10. Door 40 also includes a closing lever 114 extending therefrom which may, conveniently, be integral therewith and covered with .a piece of nylon tubing 116.

A door actuating member 118 is affixed by any convenient means to an interior wall 120 of the moisture tester so that the actuating member is fixed relative to the hopper. Two tabs, a door release tab 122 and a door closing tab 124 are integral with the actuating member and extend perpendicularly from wall 120. Tabs 122 and 124 are horizontally positioned to alternately engage or disengage door release dog 102 and closing lever 114, respectively, depending on the vertical location of hopper 40. Wall 120 has additionally affixed thereto a restraining spring 126 for resilient engagement with rib 52 on hopper 40. (See FIG. 15.)

Spring 126 has one end inserted through an opening 128 in wall 120 and is bent around a pin 130 and under a washer 132. The other end of spring 126 isbent upward forming a bite; the bite is inserted between two washers 134 and 136 mounted on a pin 138 affixed to wall 120, thus forming an upwardly extending bow 140 in spring 126. The bite is capable of relative motion between washers 134 and 136 thus varying the vertical position of the bow 140. The bow is placed for engagement by ridge 52 when hopper 40 is lowered suffi ciently.

The operation of the door catch mechanism will now be explained. In the normal, unloaded condition, hopper 40 is urged upward by springs 82. However, closing lever 114 engages tab 124 forming an upward travel stop restraining the hopper from upward movement. When sufficient material is placed in the hopper,

it will be displaced downward and lever 114 will disenstops, the upper stop being created by the action of lever 114 against tab 124 and the lower one by the action of rib 52 against spring 126. The swinging action informs the user that the correct weight of material has been placed in the hopper. f

To release the material from the hopper, the user merely pushes downward'upon the exposed parts of hopper upper section 46 against the force of spring 126. The hopper is thus displaced further downward until door release dog 102 engages door release tab 122. That engagement causes catch lever 92 to rotate about pin 96 against the force of spring 100 moving door retaining dog 104 away from latching extension 110 thus leaving door-42 free to fall away and pivot open about ,pins' 53. (See FIG. 11.) The downward travel of the hopper may be limited by the engagement of lever 92 with hopper 40 as it rotates about pin 96,

, i 126 causes the hopper to return to itsunloaded position. As it does so, dog 102 moves off tab 122, and lever 96 moves back to its normal position. (See FIG. 12.) When the hopper continues its upward motion, closinglever 114 engages door closing tab 124. The continued upward movement of the hopper after that engagement causes door 42 to pivot about pins 52 up to its closed position. As the door moves upward, oblique surface 112 on the latching extension 110 engages the exposed surface 108 of dog 104 causing lever 92 to again pivot about pin 96 against the force of spring 100. When door 42 reaches its fully closed position, lever 92 moves back to its normal position, door retaining dog 104 engaging the underside of extension 110.

A fragmentary view of a moisture tester 200 including a second sample scale 202 of this invention is shown in FIG. 16. Sample scale 202 is very similar to the sample scale 22 disclosed above and will not be described in detail, Parts similar to those insample scale 22 are similarly numbered.

Sample scale 202 includes a hopper 40 and a pair of doors 42a and 42b. A pushbutton 204 is provided for dumping the hopper contents into a cell, not shown, located directly beneath the hopper. Button 204 is mechanically linked to hopper 40 so that when the button is depressed, the hopper is moved downward and a door catch mechanism releases doors 42a and 42b. The linking mechanism may also include a downward hopper travel stop eliminating the need for a restraining spring such as spring 126. The door catch mechanism is similar to the one above described, but catch lever 92 must be disposed centrally on the hopper to engage both doors 42a and 42b. The door catch mechanism of scale 202 is located on the side of hopper 40 closest to support bracket 58.

Since two doors 42a and 42b are provided in this embodiment, it is necessary to insure that both doors are completely closed before the hopper 40 engages the upward travel stop. In order to achieve this, a closing bracket 206 is provided which is pivotally attached at its center, as by a pin 208, to bracket 58. Bracket 206,

shown in FIG. 20, has two door-closing tabs 124a and 124k extending from opposite ends thereof for engaging closing levers 114a and 114b extending from doors 42a and 42b, respectively. As'hopper 40 is urged upward by springs 82, one of closing levers 114a or 114b 8 will normally engage its corresponding tab 1240 or 124b before the other. However, the pivotal motion of bracket 206 about pin 208 will prevent that first engaging door from moving toward its closed position until the other door closing lever engages its tab. Similarly, the pivotal motion of bracket 206 will insure that equal forces will be exerted against both closing levers 114a and 114b, and thus that both doors 42a and 42b will be fully closed, when hopper 40 is at its extreme of upward travel.

' Sample scale 202 further differs from sample scale 22 in the means used to calibrate the scale. Here the knife edge inserts on bracket 58 are threaded through cantilever arms 210 extending from a bracket affixed to bracket 58. Screws 63 extend from another bracket 214 affixed to bracket 58 and are threaded through arms 210. Springs 216 are placed about screws 63. Adjustment of screws 63 together with the action of springs 216 thus varies the vertical location of inserts 60 and adjusts the calibration of the scale.

It will thus be seen that a sample scale has been provided which fulfills all of the above-mentioned objects. It will be obvious that certain modifications; of the specific embodiments shown may be made without departing from the spirit and scope of this invention. For example, the relative size, shape, and location of the various component parts of the sample scales shown could be altered without affecting their principle of operation. Details of the various mounting, catching, and latching mechanisms might be varied. Further, the sample scales of this invention might find application in instruments other than moisture testers.

While two particular embodiments of this invention are shown above, it will be understood, of course, that the invention is not to be limited thereto since many modifications may be made. It is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the true spirit and'scope of this invention.

I claim:

l. A sample scale for measuring a predetermined weight of material under test and attached to a fixed support comprising:

a hopper horizontally displaced from said fixed support for receiving a sample of said material;

a plurality of parallel support bar's, each of said bars connecting said hopper and said fixed support and being adapted for pivotal movement with respect to the points of connectionwith said hopper and said fixed support and permitting vertical motion of said hopper with respect to said fixed support;

an upward travel stop fixedly located with respect to nection when said hopper engages said upward travel stop; and

a spring connected between said first and second spring connection points restraining said hopper from downward vertical motion.

2. The sample scale of claim 1 further comprising:

' a third spring connection point attached to said hopper and located at the same vertical position of said first spring connection point;

a fourth spring connection point attached to said fixed support and located at the same vertical position of said second spring connection point; and

a; second spring connected between said first and j second spring connection points.

3. The. sample scale of claim l further comprising a downwardtravel stop fixedly located with respect to said fixed support and engaging said hopper limiting the downward travel of said hopper with respect to said fixed support. I

4. The sample scale of claim 1 further comprising:

a door. forming a lower wall of said hopper pivotally mounted on said .hopper for movement between open and closed positions;

door engagement means for maintaining said door in said closed position when said hopper is above a first predetermined vertical position; door release means for allowing said door to assume said open position 'as said hopper moves downward past said first predetermined vertical position; and

door closing means for returning said door to said closed position as said hopper moves upward past a second predetermined vertical position.

5. The sample scale of claim 4 wherein said second predetermined vertical position is located above said first predetermined vertical position.

6. The sample scale of claim 5 wherein said door engagement means comprises a first dog attached to one end of a catch lever and engaging the underside of said door when the upward travel of said hopper is limited by said travel stop, said catch lever being pivotally mounted on said hopper, and said door release means comprises a second dog attached to another end of said catch lever and a first member fixedly connected to said fixed support and engaging said second dog as said hopper moves downward past said first predetermined vertical position.

7. The sample scale of claim 6 wherein said door closing means comprises a second member attached to said door and a third member fixedly connected to said fixed support engaging said second member as said hopper moves upward past said second predetermined vertical position and pivoting said door into said closed position.

*8: The sample scale of claim 1 further comprising means for adjusting the vertical spacing between said first and second spring connection points.

9. The sample scale of claim 1 further comprising means for adjusting the horizontal spacing between,

ty of doors in said closed configuration when said hopper is above a first predetermined vertical position; door release means for allowing said plurality of doors to assume said open configuration as said hopper moves downward past said first predetermined vertical position; and

door closing means or returmng said plurality of doors to said closed configuration as said hopper moves upward past a second predetermined vertical position.

11. The sample scale of claim 10 wherein two doors form said lower hopper wall and said door closing means comprises a first member attached to the first of. said doors,-a second member attached to the second of said doors, a third member attached to a closing bar and engaging said first member as said hopper moves upward past said second predetermined vertical position, a fourth member attached to said closing bar and engaging said second member as said hopper moves upward past said second predetermined vertical position,

and a pivot connection connecting said closing bar to said fixed support at a point intermediate said third and fourth members.

12. A sample scale for measuring a predetermined weight of material under test and attached to a fixed support comprising:

a hopper horizontally displaced from said fixed support for receiving a sample of said material;

a plurality of parallel support bars, each of said bars connecting said hopper and said fixed support and being adapted for pivotal movement with respect to the points of connection with said hopper and said fixed support and permitting vertical motion of said hopper with respect to said fixed support;

an upward travel stop fixedly located with respect to said fixed support and limiting the upward travel of said hopper with respect to said fixed support; and

resilient means connected between said hopper and said fixed support for restraining said hopper from downward vertical motion.

13. The sample scale of claim 12 further comprising a downward travel stop fixedly located with respect to movement between open and closed configurations; door engagement means for maintaining said pluralisaid fixed support and limiting the downward travel of said hopper with respect to said fixed support.

14. The sample scale of claim 12 further comprising: a door forming a lower wall of said hopper mounted on said hopper for movement between open and closed positions; door engagement means for maintaining said door in said closed position when said hopper is above a first predetermined vertical position; door release means for allowing said door to assume said open position as said hoppermoves downward past said first predetermined vertical position; and door closing means for returning said door to said closed position as said hopper moves upward past a second predetermined vertical position. 

1. A sample scale for measuring a predetermined weight of material under test and attached to a fixed support comprising: a hopper horizontally displaced from said fixed support for receiving a sample of said material; a plurality of parallel support bars, each of said bars connecting said hopper and said fixed support and being adapted for pivotal movement with respect to the points of connection with said hopper and said fixed support and permitting vertical motion of said hopper with respect to said fixed support; an upward travel stop fixedly located with respect to said fixed support and engaging said hopper limiting the upward travel of said hopper with respect to said fixed support; a fist spring connection point attached to said hopper; a second spring connection point attached to said fixed support and located at a vertical position above the vertical position of said first spring connection when said hopper engages said upward travel stop; and a spring connected between said first and second spring connection points restraining said hopper from downward vertical motion.
 2. The sample scale of claim 1 further comprising: a third spring connection point attached to said hopper and located at the same vertical position of said first spring connection point; a fourth spring connection point attached to said fixed support and located at the same vertical position of said second spring connection point; and a second spring connected between said first and second spring connection points.
 3. The sample scale of claim 1 further comprising a downward travel stop fixedly located with respect to said fixed sUpport and engaging said hopper limiting the downward travel of said hopper with respect to said fixed support.
 4. The sample scale of claim 1 further comprising: a door forming a lower wall of said hopper pivotally mounted on said hopper for movement between open and closed positions; door engagement means for maintaining said door in said closed position when said hopper is above a first predetermined vertical position; door release means for allowing said door to assume said open position as said hopper moves downward past said first predetermined vertical position; and door closing means for returning said door to said closed position as said hopper moves upward past a second predetermined vertical position.
 5. The sample scale of claim 4 wherein said second predetermined vertical position is located above said first predetermined vertical position.
 6. The sample scale of claim 5 wherein said door engagement means comprises a first dog attached to one end of a catch lever and engaging the underside of said door when the upward travel of said hopper is limited by said travel stop, said catch lever being pivotally mounted on said hopper, and said door release means comprises a second dog attached to another end of said catch lever and a first member fixedly connected to said fixed support and engaging said second dog as said hopper moves downward past said first predetermined vertical position.
 7. The sample scale of claim 6 wherein said door closing means comprises a second member attached to said door and a third member fixedly connected to said fixed support engaging said second member as said hopper moves upward past said second predetermined vertical position and pivoting said door into said closed position.
 8. The sample scale of claim 1 further comprising means for adjusting the vertical spacing between said first and second spring connection points.
 9. The sample scale of claim 1 further comprising means for adjusting the horizontal spacing between said first and second spring connection points.
 10. The sample scale of claim 2 further comprising: a plurality of doors forming a lower wall of said hopper pivotally mounted on said hopper for movement between open and closed configurations; door engagement means for maintaining said plurality of doors in said closed configuration when said hopper is above a first predetermined vertical position; door release means for allowing said plurality of doors to assume said open configuration as said hopper moves downward past said first predetermined vertical position; and door closing means for returning said plurality of doors to said closed configuration as said hopper moves upward past a second predetermined vertical position.
 11. The sample scale of claim 10 wherein two doors form said lower hopper wall and said door closing means comprises a first member attached to the first of said doors, a second member attached to the second of said doors, a third member attached to a closing bar and engaging said first member as said hopper moves upward past said second predetermined vertical position, a fourth member attached to said closing bar and engaging said second member as said hopper moves upward past said second predetermined vertical position, and a pivot connection connecting said closing bar to said fixed support at a point intermediate said third and fourth members.
 12. A sample scale for measuring a predetermined weight of material under test and attached to a fixed support comprising: a hopper horizontally displaced from said fixed support for receiving a sample of said material; a plurality of parallel support bars, each of said bars connecting said hopper and said fixed support and being adapted for pivotal movement with respect to the points of connection with said hopper and said fixed support and permitting vertical motion of said hopper with respect to said fixed support; an upward travel stop fixedly located with respect to said Fixed support and limiting the upward travel of said hopper with respect to said fixed support; and resilient means connected between said hopper and said fixed support for restraining said hopper from downward vertical motion.
 13. The sample scale of claim 12 further comprising a downward travel stop fixedly located with respect to said fixed support and limiting the downward travel of said hopper with respect to said fixed support.
 14. The sample scale of claim 12 further comprising: a door forming a lower wall of said hopper mounted on said hopper for movement between open and closed positions; door engagement means for maintaining said door in said closed position when said hopper is above a first predetermined vertical position; door release means for allowing said door to assume said open position as said hopper moves downward past said first predetermined vertical position; and door closing means for returning said door to said closed position as said hopper moves upward past a second predetermined vertical position. 